1. Field of the Invention
The present invention relates to a substrate supporting device and a sputtering apparatus. Described more particularly, the invention relates to a substrate supporting device which supports a substrate in such a way that the substrate is opposed to a sputtering target in a vacuum chamber to form a coating film on the substrate by sputtering, and to a sputtering apparatus including such a substrate supporting device provided in the vacuum chamber.
2. Description of the Related Art
There are conventionally known decorated products each provided with so-called metallic decoration that provides a metallic surface in appearance on a surface (a design surface) of a substrate comprised of a resin molded article or the like. Those decorated products, as alternatives to real metal products, have been broadly used, for example, as skin materials, parts, or the like of various products and items such as automobile interior parts, furniture, building materials, home electric appliances, and mobile electronic apparatuses.
Sputtering (a sputtering method) is conventionally known as one method for providing a metallic decoration on a substrate surface, which is performed when such decorated products are produced. As is well known, the sputtering method is performed as follows. Inside a vacuum chamber of a sputtering apparatus, a substrate is arranged so as to be opposed to a sputtering target made of a film deposition material with a predetermined distance therebetween. In that condition, high-energy particles such as inert gas ions are collided against the sputtering target to allow sputtered particles such as constituent atoms and ions of the target material to fly out (emitted) from the sputtering target. Then, the sputtered particles are adhered and deposited onto a surface of the substrate to form a coating film constituted by a metal film made of the same material as that of the sputtering target. According to the sputtering method, as compared to other decorating methods using metallic coating, metal plating, or the like, the coating film is formed on the substrate with an extremely small thickness and a sufficiently strong adhesiveness. Accordingly, the sputtering method can provide a decorated product with a high quality and a high durability.
The above sputtering method, in general, uses a sputtering apparatus in which a supporting device for supporting the substrate in a removable and positionally fixed manner is disposed inside a vacuum chamber. The substrate is supported by the supporting device disposed inside the vacuum chamber such that the substrate is opposed to a sputtering target in a manner so as to be spaced apart from each other by a predetermined distance, and then sputtering is performed.
When decoration is made on the substrate by the sputtering in the condition where the substrate is supported by the conventional supporting device as above, the sputtered particles ejected from the sputtering target and traveling in an opposing direction of the substrate and the sputtering target or in a direction intersecting diagonally with the opposing direction, regardless of the traveling directions of the sputtered particles, reach a surface of the substrate that is opposed to the sputtering target in a sufficient amount and surely adhere and deposit onto the surface thereof. Consequently, the coating film is formed with an even and sufficient thickness on the surface of the substrate that is opposed to the sputtering target.
However, in the above conventional method, the sputtered particles cannot be adhered on a surface of the substrate positioned opposite to the surface which is opposed to the sputtering target. Thus, it is impossible to form a coating film at once on both of the surfaces of the substrate, which is opposed to the sputtering target and the other surface thereof.
In addition, on side surfaces of the substrate positioned adjacently to the surface opposed to the sputtering target, particularly, among them, on a side surface orthogonal to the surface of the substrate opposed to the sputtering target, substantially, only a small part of the sputtered particles traveling in the direction intersecting diagonally to the opposing direction of the substrate and the sputtering target is adhered and deposited. Therefore, it is difficult to sufficiently secure the film thickness of the coating film formed on the side surfaces.
Furthermore, an incident angle of the sputtered particles to those side surfaces is extremely small. Thus, due to a so-called self-shadowing effect, the sputtered particles are deposited not in a layer form but in a columnar form. Accordingly, there occur defects such as an uneven thickness of the coating film and a reduction in adhesiveness of the coating film to the substrate. Moreover, if no undercoat layer is formed between the coating film and the substrate, when a topcoat layer is formed on a side opposite to a side of the substrate of the coating film, a component part contained in the topcoat layer (e.g. an organic solvent such as thinner) comes in contact with the substrate through minute holes or the like generated in a thinner part of the coating film. Thereby, there may be caused a risk of deterioration of a quality that may allow erosion of the substrate.
In JP-A-05-320893 and JP-A-05-51740, for example, there is proposed a technique in which a substrate is disposed in a vacuum chamber such that the substrate is supported rotatably around an axis, and along with a rotation around the axis, a portion of the substrate other than the surface thereof opposed to a sputtering target is positioned so as to be opposed at an angle with the sputtering target or parallel to the sputtering target. An expression of being “opposed at angle with the sputtering target or parallel to the sputtering target” means a condition in which a predetermined surface of the substrate is positioned so as to form an angle of from 0 degree to less than 90 degrees with respect to a surface of the sputtering target from which the sputtered particles are emitted. The expression is hereinafter used in the same meaning. In the above technique, however, the surface of the substrate that is allowed to be opposed at an angle or parallel to the sputtering target is limited to a certain surface. Thus, the technique does not allow all surfaces of the substrate to be opposed at an angle or parallel to the sputtering target. Accordingly, it is absolutely impossible to solve all the various problems described above.